These are my notes to myself for adjusting the Z Offset for the BLTouch for my Ender 3V2 Printer.

I'm running OctoPrint and Klipper Firmware.

1. Let the bed cool to room temperature.
2. Get out a sheet of paper.
3. G28
4. G90 — Switch to absolute position mode.
5. G1 Z3 — Move down to z +3mm.
6. Verify that we aren't about to hit the bed.
7. Now, keep moving down (G1 Z2 etc.) until the get to the depth where the paper test passes.
8. Set the BLTouch offset to current_bltouch_z_offset - current_z_position — So if our absolute Z position goes below zero, we want to add that difference to the existing offset.
9. Set that value in printer.cfg and save it.
10. restart
11. Repeat again, until Z0 is at the right position.
12. Do a test print to confirm.
13. Once the depth seems right, you probably want to do a BED_MESH_CALIBRATE again.